The hot and dry season in Southeast Asia is the best time to enjoy mangoes. Get the sweetest ones you can find to make this lovely cold snack that will make you forget the heat and humidity even if only for a short while.How much sugar you need to stir into the coconut milk depends on how sweet your mangoes are. If the mangoes are really sweet, tone down on the sugar.
Dump the sago into a sauce pan and cover with four cups of water.
Cook over medium-high heat, stirring often, until plump and translucent but with the centers still an opaque white.
Drain the sago in a colander and rinse under the tap before dumping into a bowl of iced water. Leave until cool.
Over medium heat, scald the coconut milk with the sugar, a pinch of salt and the pandan leaf. Stir well to make sure the sugar and salt are completely dissolved.
Drain the sago well and, with the heat off, stir into the coconut milk. Cool, transfer to a covered container and chill in the fridge.
Chill the mango cubes and puree as well.
To assemble, ladle sago / coconut mixture into bowls or mugs, spoon mango puree on top, and repeat the layering until the bowls or mugs are almost full.